1. Field of the Invention
The present invention relates, in general, to methods and systems of data storage management, and more particularly, to a design for automatically linking partitions on storage media.
2. Relevant Background
Modern storage media devices (e.g., magnetic storage tapes, cassettes, multi-volume cartridges) oftentimes used in large-scale storage management applications hold hundreds to thousands of gigabytes of data. To better utilize this immense data-storage capacity, multiple data objects (e.g., host files or virtual tape volumes) are “stacked” on a single storage tape, with each set of data having different invalidation (e.g., expiration) parameters. When a particular data set expires, it creates “gaps” or wasted space on the tape. Over time, the wasted space becomes so large that the tape must be reclaimed. Reclaiming involves copying the valid data remaining on the tape and moving it to a contiguous space, usually at the beginning of the tape, such that the previously wasted space becomes useful for rewriting.
Discrete tape partitioning was developed to address the time and expense required in reclaiming storage tapes. Discrete tape partitioning involves dividing a storage tape into multiple discrete partitions such that once data has expired from a particular partition, that partition may be rewritten. While discrete tape partitioning has existed for many years, it has significant drawbacks and has been unpopular with developers. For instance, in discrete partitioning, only a host (e.g., a host application running on a mainframe server) may track which partitions contain valid data as well as the locations of the data objects or host files as stored within the tape partitions. Because each partition is separate and distinct, the host application must be involved in processing at the end of each partition in order to properly direct an archive device (e.g., a tape drive) to the next applicable partition in both read and write operations. If the archive device is reading data from the tape, the host must direct the archive device to the next partition that contains data associated with the host file being read. If the archive device is writing data to the tape, the host must direct the device to the next partition that is free of valid data and, therefore, available for rewriting.